/*
 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
 *
 * Floating-point emulation code
 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2, or (at your option)
 *    any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
/*
 * BEGIN_DESC
 *
 *  File:
 *      @(#)    pa/spmath/fmpyfadd.c            $Revision: 1.1 $
 *
 *  Purpose:
 *      Double Floating-point Multiply Fused Add
 *      Double Floating-point Multiply Negate Fused Add
 *      Single Floating-point Multiply Fused Add
 *      Single Floating-point Multiply Negate Fused Add
 *
 *  External Interfaces:
 *      dbl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
 *      dbl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
 *      sgl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
 *      sgl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
 *
 *  Internal Interfaces:
 *
 *  Theory:
 *      <<please update with a overview of the operation of this file>>
 *
 * END_DESC
*/


#include "float.h"
#include "sgl_float.h"
#include "dbl_float.h"


/*
 *  Double Floating-point Multiply Fused Add
 */

int
dbl_fmpyfadd(
            dbl_floating_point *src1ptr,
            dbl_floating_point *src2ptr,
            dbl_floating_point *src3ptr,
            unsigned int *status,
            dbl_floating_point *dstptr)
{
        unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2, opnd3p1, opnd3p2;
        register unsigned int tmpresp1, tmpresp2, tmpresp3, tmpresp4;
        unsigned int rightp1, rightp2, rightp3, rightp4;
        unsigned int resultp1, resultp2 = 0, resultp3 = 0, resultp4 = 0;
        register int mpy_exponent, add_exponent, count;
        boolean inexact = FALSE, is_tiny = FALSE;

        unsigned int signlessleft1, signlessright1, save;
        register int result_exponent, diff_exponent;
        int sign_save, jumpsize;
        
        Dbl_copyfromptr(src1ptr,opnd1p1,opnd1p2);
        Dbl_copyfromptr(src2ptr,opnd2p1,opnd2p2);
        Dbl_copyfromptr(src3ptr,opnd3p1,opnd3p2);

        /* 
         * set sign bit of result of multiply
         */
        if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1)) 
                Dbl_setnegativezerop1(resultp1); 
        else Dbl_setzerop1(resultp1);

        /*
         * Generate multiply exponent 
         */
        mpy_exponent = Dbl_exponent(opnd1p1) + Dbl_exponent(opnd2p1) - DBL_BIAS;

        /*
         * check first operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd1p1)) {
                if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
                        if (Dbl_isnotnan(opnd2p1,opnd2p2) &&
                            Dbl_isnotnan(opnd3p1,opnd3p2)) {
                                if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
                                        /* 
                                         * invalid since operands are infinity 
                                         * and zero 
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }
                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
                                    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd1p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled()) 
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd1p1);
                        }
                        /* 
                         * is second operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd2p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd2p1);
                                Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check second operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd2p1)) {
                if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
                        if (Dbl_isnotnan(opnd3p1,opnd3p2)) {
                                if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
                                        /* 
                                         * invalid since multiply operands are
                                         * zero & infinity
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(opnd2p1,opnd2p2);
                                        Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
                                    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd2p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd2p1);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check third operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd3p1)) {
                if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
                        /* return infinity */
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                } else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * Generate multiply mantissa
         */
        if (Dbl_isnotzero_exponent(opnd1p1)) {
                /* set hidden bit */
                Dbl_clear_signexponent_set_hidden(opnd1p1);
        }
        else {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Dbl_or_signs(opnd3p1,resultp1);
                                } else {
                                        Dbl_and_signs(opnd3p1,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Dbl_iszero_exponent(opnd3p1) &&
                                 Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Dbl_signextendedsign(opnd3p1);
                                result_exponent = 0;
                                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                                Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
                                Dbl_set_sign(opnd3p1,/*using*/sign_save);
                                Dbl_setwrapped_exponent(opnd3p1,result_exponent,
                                                        unfl);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized, adjust exponent */
                Dbl_clear_signexponent(opnd1p1);
                Dbl_leftshiftby1(opnd1p1,opnd1p2);
                Dbl_normalize(opnd1p1,opnd1p2,mpy_exponent);
        }
        /* opnd2 needs to have hidden bit set with msb in hidden bit */
        if (Dbl_isnotzero_exponent(opnd2p1)) {
                Dbl_clear_signexponent_set_hidden(opnd2p1);
        }
        else {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Dbl_or_signs(opnd3p1,resultp1);
                                } else {
                                        Dbl_and_signs(opnd3p1,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Dbl_iszero_exponent(opnd3p1) &&
                            Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Dbl_signextendedsign(opnd3p1);
                                result_exponent = 0;
                                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                                Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
                                Dbl_set_sign(opnd3p1,/*using*/sign_save);
                                Dbl_setwrapped_exponent(opnd3p1,result_exponent,
                                                        unfl);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized; want to normalize */
                Dbl_clear_signexponent(opnd2p1);
                Dbl_leftshiftby1(opnd2p1,opnd2p2);
                Dbl_normalize(opnd2p1,opnd2p2,mpy_exponent);
        }

        /* Multiply the first two source mantissas together */

        /* 
         * The intermediate result will be kept in tmpres,
         * which needs enough room for 106 bits of mantissa,
         * so lets call it a Double extended.
         */
        Dblext_setzero(tmpresp1,tmpresp2,tmpresp3,tmpresp4);

        /* 
         * Four bits at a time are inspected in each loop, and a 
         * simple shift and add multiply algorithm is used. 
         */ 
        for (count = DBL_P-1; count >= 0; count -= 4) {
                Dblext_rightshiftby4(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
                if (Dbit28p2(opnd1p2)) {
                        /* Fourword_add should be an ADD followed by 3 ADDC's */
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4, 
                         opnd2p1<<3 | opnd2p2>>29, opnd2p2<<3, 0, 0);
                }
                if (Dbit29p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1<<2 | opnd2p2>>30, opnd2p2<<2, 0, 0);
                }
                if (Dbit30p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1<<1 | opnd2p2>>31, opnd2p2<<1, 0, 0);
                }
                if (Dbit31p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1, opnd2p2, 0, 0);
                }
                Dbl_rightshiftby4(opnd1p1,opnd1p2);
        }
        if (Is_dexthiddenoverflow(tmpresp1)) {
                /* result mantissa >= 2 (mantissa overflow) */
                mpy_exponent++;
                Dblext_rightshiftby1(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
        }

        /*
         * Restore the sign of the mpy result which was saved in resultp1.
         * The exponent will continue to be kept in mpy_exponent.
         */
        Dblext_set_sign(tmpresp1,Dbl_sign(resultp1));

        /* 
         * No rounding is required, since the result of the multiply
         * is exact in the extended format.
         */

        /*
         * Now we are ready to perform the add portion of the operation.
         *
         * The exponents need to be kept as integers for now, since the
         * multiply result might not fit into the exponent field.  We
         * can't overflow or underflow because of this yet, since the
         * add could bring the final result back into range.
         */
        add_exponent = Dbl_exponent(opnd3p1);

        /*
         * Check for denormalized or zero add operand.
         */
        if (add_exponent == 0) {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
                        /* right is zero */
                        /* Left can't be zero and must be result.
                         *
                         * The final result is now in tmpres and mpy_exponent,
                         * and needs to be rounded and squeezed back into
                         * double precision format from double extended.
                         */
                        result_exponent = mpy_exponent;
                        Dblext_copy(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                                resultp1,resultp2,resultp3,resultp4);
                        sign_save = Dbl_signextendedsign(resultp1);/*save sign*/
                        goto round;
                }

                /* 
                 * Neither are zeroes.  
                 * Adjust exponent and normalize add operand.
                 */
                sign_save = Dbl_signextendedsign(opnd3p1);      /* save sign */
                Dbl_clear_signexponent(opnd3p1);
                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                Dbl_normalize(opnd3p1,opnd3p2,add_exponent);
                Dbl_set_sign(opnd3p1,sign_save);        /* restore sign */
        } else {
                Dbl_clear_exponent_set_hidden(opnd3p1);
        }
        /*
         * Copy opnd3 to the double extended variable called right.
         */
        Dbl_copyto_dblext(opnd3p1,opnd3p2,rightp1,rightp2,rightp3,rightp4);

        /*
         * A zero "save" helps discover equal operands (for later),
         * and is used in swapping operands (if needed).
         */
        Dblext_xortointp1(tmpresp1,rightp1,/*to*/save);

        /*
         * Compare magnitude of operands.
         */
        Dblext_copytoint_exponentmantissap1(tmpresp1,signlessleft1);
        Dblext_copytoint_exponentmantissap1(rightp1,signlessright1);
        if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
            Dblext_ismagnitudeless(tmpresp2,rightp2,signlessleft1,signlessright1)){
                /*
                 * Set the left operand to the larger one by XOR swap.
                 * First finish the first word "save".
                 */
                Dblext_xorfromintp1(save,rightp1,/*to*/rightp1);
                Dblext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
                Dblext_swap_lower(tmpresp2,tmpresp3,tmpresp4,
                        rightp2,rightp3,rightp4);
                /* also setup exponents used in rest of routine */
                diff_exponent = add_exponent - mpy_exponent;
                result_exponent = add_exponent;
        } else {
                /* also setup exponents used in rest of routine */
                diff_exponent = mpy_exponent - add_exponent;
                result_exponent = mpy_exponent;
        }
        /* Invariant: left is not smaller than right. */

        /*
         * Special case alignment of operands that would force alignment
         * beyond the extent of the extension.  A further optimization
         * could special case this but only reduces the path length for
         * this infrequent case.
         */
        if (diff_exponent > DBLEXT_THRESHOLD) {
                diff_exponent = DBLEXT_THRESHOLD;
        }

        /* Align right operand by shifting it to the right */
        Dblext_clear_sign(rightp1);
        Dblext_right_align(rightp1,rightp2,rightp3,rightp4,
                /*shifted by*/diff_exponent);
        
        /* Treat sum and difference of the operands separately. */
        if ((int)save < 0) {
                /*
                 * Difference of the two operands.  Overflow can occur if the
                 * multiply overflowed.  A borrow can occur out of the hidden
                 * bit and force a post normalization phase.
                 */
                Dblext_subtract(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                        rightp1,rightp2,rightp3,rightp4,
                        resultp1,resultp2,resultp3,resultp4);
                sign_save = Dbl_signextendedsign(resultp1);
                if (Dbl_iszero_hidden(resultp1)) {
                        /* Handle normalization */
                /* A straight foward algorithm would now shift the
                 * result and extension left until the hidden bit
                 * becomes one.  Not all of the extension bits need
                 * participate in the shift.  Only the two most 
                 * significant bits (round and guard) are needed.
                 * If only a single shift is needed then the guard
                 * bit becomes a significant low order bit and the
                 * extension must participate in the rounding.
                 * If more than a single shift is needed, then all
                 * bits to the right of the guard bit are zeros, 
                 * and the guard bit may or may not be zero. */
                        Dblext_leftshiftby1(resultp1,resultp2,resultp3,
                                resultp4);

                        /* Need to check for a zero result.  The sign and
                         * exponent fields have already been zeroed.  The more
                         * efficient test of the full object can be used.
                         */
                         if(Dblext_iszero(resultp1,resultp2,resultp3,resultp4)){
                                /* Must have been "x-x" or "x+(-x)". */
                                if (Is_rounding_mode(ROUNDMINUS))
                                        Dbl_setone_sign(resultp1);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                        result_exponent--;

                        /* Look to see if normalization is finished. */
                        if (Dbl_isone_hidden(resultp1)) {
                                /* No further normalization is needed */
                                goto round;
                        }

                        /* Discover first one bit to determine shift amount.
                         * Use a modified binary search.  We have already
                         * shifted the result one position right and still
                         * not found a one so the remainder of the extension
                         * must be zero and simplifies rounding. */
                        /* Scan bytes */
                        while (Dbl_iszero_hiddenhigh7mantissa(resultp1)) {
                                Dblext_leftshiftby8(resultp1,resultp2,resultp3,resultp4);
                                result_exponent -= 8;
                        }
                        /* Now narrow it down to the nibble */
                        if (Dbl_iszero_hiddenhigh3mantissa(resultp1)) {
                                /* The lower nibble contains the
                                 * normalizing one */
                                Dblext_leftshiftby4(resultp1,resultp2,resultp3,resultp4);
                                result_exponent -= 4;
                        }
                        /* Select case where first bit is set (already
                         * normalized) otherwise select the proper shift. */
                        jumpsize = Dbl_hiddenhigh3mantissa(resultp1);
                        if (jumpsize <= 7) switch(jumpsize) {
                        case 1:
                                Dblext_leftshiftby3(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 3;
                                break;
                        case 2:
                        case 3:
                                Dblext_leftshiftby2(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 2;
                                break;
                        case 4:
                        case 5:
                        case 6:
                        case 7:
                                Dblext_leftshiftby1(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 1;
                                break;
                        }
                } /* end if (hidden...)... */
        /* Fall through and round */
        } /* end if (save < 0)... */
        else {
                /* Add magnitudes */
                Dblext_addition(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                        rightp1,rightp2,rightp3,rightp4,
                        /*to*/resultp1,resultp2,resultp3,resultp4);
                sign_save = Dbl_signextendedsign(resultp1);
                if (Dbl_isone_hiddenoverflow(resultp1)) {
                        /* Prenormalization required. */
                        Dblext_arithrightshiftby1(resultp1,resultp2,resultp3,
                                resultp4);
                        result_exponent++;
                } /* end if hiddenoverflow... */
        } /* end else ...add magnitudes... */

        /* Round the result.  If the extension and lower two words are
         * all zeros, then the result is exact.  Otherwise round in the
         * correct direction.  Underflow is possible. If a postnormalization
         * is necessary, then the mantissa is all zeros so no shift is needed.
         */
  round:
        if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
                Dblext_denormalize(resultp1,resultp2,resultp3,resultp4,
                        result_exponent,is_tiny);
        }
        Dbl_set_sign(resultp1,/*using*/sign_save);
        if (Dblext_isnotzero_mantissap3(resultp3) || 
            Dblext_isnotzero_mantissap4(resultp4)) {
                inexact = TRUE;
                switch(Rounding_mode()) {
                case ROUNDNEAREST: /* The default. */
                        if (Dblext_isone_highp3(resultp3)) {
                                /* at least 1/2 ulp */
                                if (Dblext_isnotzero_low31p3(resultp3) ||
                                    Dblext_isnotzero_mantissap4(resultp4) ||
                                    Dblext_isone_lowp2(resultp2)) {
                                        /* either exactly half way and odd or
                                         * more than 1/2ulp */
                                        Dbl_increment(resultp1,resultp2);
                                }
                        }
                        break;

                case ROUNDPLUS:
                        if (Dbl_iszero_sign(resultp1)) {
                                /* Round up positive results */
                                Dbl_increment(resultp1,resultp2);
                        }
                        break;
            
                case ROUNDMINUS:
                        if (Dbl_isone_sign(resultp1)) {
                                /* Round down negative results */
                                Dbl_increment(resultp1,resultp2);
                        }
            
                case ROUNDZERO:;
                        /* truncate is simple */
                } /* end switch... */
                if (Dbl_isone_hiddenoverflow(resultp1)) result_exponent++;
        }
        if (result_exponent >= DBL_INFINITY_EXPONENT) {
                /* trap if OVERFLOWTRAP enabled */
                if (Is_overflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Dbl_setwrapped_exponent(resultp1,result_exponent,ovfl);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_OVERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return (OPC_2E_OVERFLOWEXCEPTION);
                }
                inexact = TRUE;
                Set_overflowflag();
                /* set result to infinity or largest number */
                Dbl_setoverflow(resultp1,resultp2);

        } else if (result_exponent <= 0) {      /* underflow case */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_UNDERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return(OPC_2E_UNDERFLOWEXCEPTION);
                }
                else if (inexact && is_tiny) Set_underflowflag();
        }
        else Dbl_set_exponent(resultp1,result_exponent);
        Dbl_copytoptr(resultp1,resultp2,dstptr);
        if (inexact) 
                if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
                else Set_inexactflag();
        return(NOEXCEPTION);
}

/*
 *  Double Floating-point Multiply Negate Fused Add
 */

dbl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)

dbl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
unsigned int *status;
{
        unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2, opnd3p1, opnd3p2;
        register unsigned int tmpresp1, tmpresp2, tmpresp3, tmpresp4;
        unsigned int rightp1, rightp2, rightp3, rightp4;
        unsigned int resultp1, resultp2 = 0, resultp3 = 0, resultp4 = 0;
        register int mpy_exponent, add_exponent, count;
        boolean inexact = FALSE, is_tiny = FALSE;

        unsigned int signlessleft1, signlessright1, save;
        register int result_exponent, diff_exponent;
        int sign_save, jumpsize;
        
        Dbl_copyfromptr(src1ptr,opnd1p1,opnd1p2);
        Dbl_copyfromptr(src2ptr,opnd2p1,opnd2p2);
        Dbl_copyfromptr(src3ptr,opnd3p1,opnd3p2);

        /* 
         * set sign bit of result of multiply
         */
        if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1)) 
                Dbl_setzerop1(resultp1);
        else
                Dbl_setnegativezerop1(resultp1); 

        /*
         * Generate multiply exponent 
         */
        mpy_exponent = Dbl_exponent(opnd1p1) + Dbl_exponent(opnd2p1) - DBL_BIAS;

        /*
         * check first operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd1p1)) {
                if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
                        if (Dbl_isnotnan(opnd2p1,opnd2p2) &&
                            Dbl_isnotnan(opnd3p1,opnd3p2)) {
                                if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
                                        /* 
                                         * invalid since operands are infinity 
                                         * and zero 
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }
                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
                                    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd1p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled()) 
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd1p1);
                        }
                        /* 
                         * is second operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd2p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd2p1);
                                Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check second operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd2p1)) {
                if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
                        if (Dbl_isnotnan(opnd3p1,opnd3p2)) {
                                if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
                                        /* 
                                         * invalid since multiply operands are
                                         * zero & infinity
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(opnd2p1,opnd2p2);
                                        Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
                                    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Dbl_makequietnan(resultp1,resultp2);
                                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd2p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd2p1);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Dbl_is_signalingnan(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check third operand for NaN's or infinity
         */
        if (Dbl_isinfinity_exponent(opnd3p1)) {
                if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
                        /* return infinity */
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                } else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Dbl_isone_signaling(opnd3p1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Dbl_set_quiet(opnd3p1);
                        }
                        /*
                         * return quiet NaN
                         */
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * Generate multiply mantissa
         */
        if (Dbl_isnotzero_exponent(opnd1p1)) {
                /* set hidden bit */
                Dbl_clear_signexponent_set_hidden(opnd1p1);
        }
        else {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Dbl_or_signs(opnd3p1,resultp1);
                                } else {
                                        Dbl_and_signs(opnd3p1,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Dbl_iszero_exponent(opnd3p1) &&
                                 Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Dbl_signextendedsign(opnd3p1);
                                result_exponent = 0;
                                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                                Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
                                Dbl_set_sign(opnd3p1,/*using*/sign_save);
                                Dbl_setwrapped_exponent(opnd3p1,result_exponent,
                                                        unfl);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized, adjust exponent */
                Dbl_clear_signexponent(opnd1p1);
                Dbl_leftshiftby1(opnd1p1,opnd1p2);
                Dbl_normalize(opnd1p1,opnd1p2,mpy_exponent);
        }
        /* opnd2 needs to have hidden bit set with msb in hidden bit */
        if (Dbl_isnotzero_exponent(opnd2p1)) {
                Dbl_clear_signexponent_set_hidden(opnd2p1);
        }
        else {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {

                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Dbl_or_signs(opnd3p1,resultp1);
                                } else {
                                        Dbl_and_signs(opnd3p1,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Dbl_iszero_exponent(opnd3p1) &&
                            Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Dbl_signextendedsign(opnd3p1);
                                result_exponent = 0;
                                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                                Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
                                Dbl_set_sign(opnd3p1,/*using*/sign_save);
                                Dbl_setwrapped_exponent(opnd3p1,result_exponent,
                                                        unfl);
                                Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized; want to normalize */
                Dbl_clear_signexponent(opnd2p1);
                Dbl_leftshiftby1(opnd2p1,opnd2p2);
                Dbl_normalize(opnd2p1,opnd2p2,mpy_exponent);
        }

        /* Multiply the first two source mantissas together */

        /* 
         * The intermediate result will be kept in tmpres,
         * which needs enough room for 106 bits of mantissa,
         * so lets call it a Double extended.
         */
        Dblext_setzero(tmpresp1,tmpresp2,tmpresp3,tmpresp4);

        /* 
         * Four bits at a time are inspected in each loop, and a 
         * simple shift and add multiply algorithm is used. 
         */ 
        for (count = DBL_P-1; count >= 0; count -= 4) {
                Dblext_rightshiftby4(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
                if (Dbit28p2(opnd1p2)) {
                        /* Fourword_add should be an ADD followed by 3 ADDC's */
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4, 
                         opnd2p1<<3 | opnd2p2>>29, opnd2p2<<3, 0, 0);
                }
                if (Dbit29p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1<<2 | opnd2p2>>30, opnd2p2<<2, 0, 0);
                }
                if (Dbit30p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1<<1 | opnd2p2>>31, opnd2p2<<1, 0, 0);
                }
                if (Dbit31p2(opnd1p2)) {
                        Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
                         opnd2p1, opnd2p2, 0, 0);
                }
                Dbl_rightshiftby4(opnd1p1,opnd1p2);
        }
        if (Is_dexthiddenoverflow(tmpresp1)) {
                /* result mantissa >= 2 (mantissa overflow) */
                mpy_exponent++;
                Dblext_rightshiftby1(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
        }

        /*
         * Restore the sign of the mpy result which was saved in resultp1.
         * The exponent will continue to be kept in mpy_exponent.
         */
        Dblext_set_sign(tmpresp1,Dbl_sign(resultp1));

        /* 
         * No rounding is required, since the result of the multiply
         * is exact in the extended format.
         */

        /*
         * Now we are ready to perform the add portion of the operation.
         *
         * The exponents need to be kept as integers for now, since the
         * multiply result might not fit into the exponent field.  We
         * can't overflow or underflow because of this yet, since the
         * add could bring the final result back into range.
         */
        add_exponent = Dbl_exponent(opnd3p1);

        /*
         * Check for denormalized or zero add operand.
         */
        if (add_exponent == 0) {
                /* check for zero */
                if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
                        /* right is zero */
                        /* Left can't be zero and must be result.
                         *
                         * The final result is now in tmpres and mpy_exponent,
                         * and needs to be rounded and squeezed back into
                         * double precision format from double extended.
                         */
                        result_exponent = mpy_exponent;
                        Dblext_copy(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                                resultp1,resultp2,resultp3,resultp4);
                        sign_save = Dbl_signextendedsign(resultp1);/*save sign*/
                        goto round;
                }

                /* 
                 * Neither are zeroes.  
                 * Adjust exponent and normalize add operand.
                 */
                sign_save = Dbl_signextendedsign(opnd3p1);      /* save sign */
                Dbl_clear_signexponent(opnd3p1);
                Dbl_leftshiftby1(opnd3p1,opnd3p2);
                Dbl_normalize(opnd3p1,opnd3p2,add_exponent);
                Dbl_set_sign(opnd3p1,sign_save);        /* restore sign */
        } else {
                Dbl_clear_exponent_set_hidden(opnd3p1);
        }
        /*
         * Copy opnd3 to the double extended variable called right.
         */
        Dbl_copyto_dblext(opnd3p1,opnd3p2,rightp1,rightp2,rightp3,rightp4);

        /*
         * A zero "save" helps discover equal operands (for later),
         * and is used in swapping operands (if needed).
         */
        Dblext_xortointp1(tmpresp1,rightp1,/*to*/save);

        /*
         * Compare magnitude of operands.
         */
        Dblext_copytoint_exponentmantissap1(tmpresp1,signlessleft1);
        Dblext_copytoint_exponentmantissap1(rightp1,signlessright1);
        if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
            Dblext_ismagnitudeless(tmpresp2,rightp2,signlessleft1,signlessright1)){
                /*
                 * Set the left operand to the larger one by XOR swap.
                 * First finish the first word "save".
                 */
                Dblext_xorfromintp1(save,rightp1,/*to*/rightp1);
                Dblext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
                Dblext_swap_lower(tmpresp2,tmpresp3,tmpresp4,
                        rightp2,rightp3,rightp4);
                /* also setup exponents used in rest of routine */
                diff_exponent = add_exponent - mpy_exponent;
                result_exponent = add_exponent;
        } else {
                /* also setup exponents used in rest of routine */
                diff_exponent = mpy_exponent - add_exponent;
                result_exponent = mpy_exponent;
        }
        /* Invariant: left is not smaller than right. */

        /*
         * Special case alignment of operands that would force alignment
         * beyond the extent of the extension.  A further optimization
         * could special case this but only reduces the path length for
         * this infrequent case.
         */
        if (diff_exponent > DBLEXT_THRESHOLD) {
                diff_exponent = DBLEXT_THRESHOLD;
        }

        /* Align right operand by shifting it to the right */
        Dblext_clear_sign(rightp1);
        Dblext_right_align(rightp1,rightp2,rightp3,rightp4,
                /*shifted by*/diff_exponent);
        
        /* Treat sum and difference of the operands separately. */
        if ((int)save < 0) {
                /*
                 * Difference of the two operands.  Overflow can occur if the
                 * multiply overflowed.  A borrow can occur out of the hidden
                 * bit and force a post normalization phase.
                 */
                Dblext_subtract(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                        rightp1,rightp2,rightp3,rightp4,
                        resultp1,resultp2,resultp3,resultp4);
                sign_save = Dbl_signextendedsign(resultp1);
                if (Dbl_iszero_hidden(resultp1)) {
                        /* Handle normalization */
                /* A straight foward algorithm would now shift the
                 * result and extension left until the hidden bit
                 * becomes one.  Not all of the extension bits need
                 * participate in the shift.  Only the two most 
                 * significant bits (round and guard) are needed.
                 * If only a single shift is needed then the guard
                 * bit becomes a significant low order bit and the
                 * extension must participate in the rounding.
                 * If more than a single shift is needed, then all
                 * bits to the right of the guard bit are zeros, 
                 * and the guard bit may or may not be zero. */
                        Dblext_leftshiftby1(resultp1,resultp2,resultp3,
                                resultp4);

                        /* Need to check for a zero result.  The sign and
                         * exponent fields have already been zeroed.  The more
                         * efficient test of the full object can be used.
                         */
                         if (Dblext_iszero(resultp1,resultp2,resultp3,resultp4)) {
                                /* Must have been "x-x" or "x+(-x)". */
                                if (Is_rounding_mode(ROUNDMINUS))
                                        Dbl_setone_sign(resultp1);
                                Dbl_copytoptr(resultp1,resultp2,dstptr);
                                return(NOEXCEPTION);
                        }
                        result_exponent--;

                        /* Look to see if normalization is finished. */
                        if (Dbl_isone_hidden(resultp1)) {
                                /* No further normalization is needed */
                                goto round;
                        }

                        /* Discover first one bit to determine shift amount.
                         * Use a modified binary search.  We have already
                         * shifted the result one position right and still
                         * not found a one so the remainder of the extension
                         * must be zero and simplifies rounding. */
                        /* Scan bytes */
                        while (Dbl_iszero_hiddenhigh7mantissa(resultp1)) {
                                Dblext_leftshiftby8(resultp1,resultp2,resultp3,resultp4);
                                result_exponent -= 8;
                        }
                        /* Now narrow it down to the nibble */
                        if (Dbl_iszero_hiddenhigh3mantissa(resultp1)) {
                                /* The lower nibble contains the
                                 * normalizing one */
                                Dblext_leftshiftby4(resultp1,resultp2,resultp3,resultp4);
                                result_exponent -= 4;
                        }
                        /* Select case where first bit is set (already
                         * normalized) otherwise select the proper shift. */
                        jumpsize = Dbl_hiddenhigh3mantissa(resultp1);
                        if (jumpsize <= 7) switch(jumpsize) {
                        case 1:
                                Dblext_leftshiftby3(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 3;
                                break;
                        case 2:
                        case 3:
                                Dblext_leftshiftby2(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 2;
                                break;
                        case 4:
                        case 5:
                        case 6:
                        case 7:
                                Dblext_leftshiftby1(resultp1,resultp2,resultp3,
                                        resultp4);
                                result_exponent -= 1;
                                break;
                        }
                } /* end if (hidden...)... */
        /* Fall through and round */
        } /* end if (save < 0)... */
        else {
                /* Add magnitudes */
                Dblext_addition(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
                        rightp1,rightp2,rightp3,rightp4,
                        /*to*/resultp1,resultp2,resultp3,resultp4);
                sign_save = Dbl_signextendedsign(resultp1);
                if (Dbl_isone_hiddenoverflow(resultp1)) {
                        /* Prenormalization required. */
                        Dblext_arithrightshiftby1(resultp1,resultp2,resultp3,
                                resultp4);
                        result_exponent++;
                } /* end if hiddenoverflow... */
        } /* end else ...add magnitudes... */

        /* Round the result.  If the extension and lower two words are
         * all zeros, then the result is exact.  Otherwise round in the
         * correct direction.  Underflow is possible. If a postnormalization
         * is necessary, then the mantissa is all zeros so no shift is needed.
         */
  round:
        if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
                Dblext_denormalize(resultp1,resultp2,resultp3,resultp4,
                        result_exponent,is_tiny);
        }
        Dbl_set_sign(resultp1,/*using*/sign_save);
        if (Dblext_isnotzero_mantissap3(resultp3) || 
            Dblext_isnotzero_mantissap4(resultp4)) {
                inexact = TRUE;
                switch(Rounding_mode()) {
                case ROUNDNEAREST: /* The default. */
                        if (Dblext_isone_highp3(resultp3)) {
                                /* at least 1/2 ulp */
                                if (Dblext_isnotzero_low31p3(resultp3) ||
                                    Dblext_isnotzero_mantissap4(resultp4) ||
                                    Dblext_isone_lowp2(resultp2)) {
                                        /* either exactly half way and odd or
                                         * more than 1/2ulp */
                                        Dbl_increment(resultp1,resultp2);
                                }
                        }
                        break;

                case ROUNDPLUS:
                        if (Dbl_iszero_sign(resultp1)) {
                                /* Round up positive results */
                                Dbl_increment(resultp1,resultp2);
                        }
                        break;
            
                case ROUNDMINUS:
                        if (Dbl_isone_sign(resultp1)) {
                                /* Round down negative results */
                                Dbl_increment(resultp1,resultp2);
                        }
            
                case ROUNDZERO:;
                        /* truncate is simple */
                } /* end switch... */
                if (Dbl_isone_hiddenoverflow(resultp1)) result_exponent++;
        }
        if (result_exponent >= DBL_INFINITY_EXPONENT) {
                /* Overflow */
                if (Is_overflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Dbl_setwrapped_exponent(resultp1,result_exponent,ovfl);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_OVERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return (OPC_2E_OVERFLOWEXCEPTION);
                }
                inexact = TRUE;
                Set_overflowflag();
                Dbl_setoverflow(resultp1,resultp2);
        } else if (result_exponent <= 0) {      /* underflow case */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
                        Dbl_copytoptr(resultp1,resultp2,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_UNDERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return(OPC_2E_UNDERFLOWEXCEPTION);
                }
                else if (inexact && is_tiny) Set_underflowflag();
        }
        else Dbl_set_exponent(resultp1,result_exponent);
        Dbl_copytoptr(resultp1,resultp2,dstptr);
        if (inexact) 
                if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
                else Set_inexactflag();
        return(NOEXCEPTION);
}

/*
 *  Single Floating-point Multiply Fused Add
 */

sgl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)

sgl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
unsigned int *status;
{
        unsigned int opnd1, opnd2, opnd3;
        register unsigned int tmpresp1, tmpresp2;
        unsigned int rightp1, rightp2;
        unsigned int resultp1, resultp2 = 0;
        register int mpy_exponent, add_exponent, count;
        boolean inexact = FALSE, is_tiny = FALSE;

        unsigned int signlessleft1, signlessright1, save;
        register int result_exponent, diff_exponent;
        int sign_save, jumpsize;
        
        Sgl_copyfromptr(src1ptr,opnd1);
        Sgl_copyfromptr(src2ptr,opnd2);
        Sgl_copyfromptr(src3ptr,opnd3);

        /* 
         * set sign bit of result of multiply
         */
        if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) 
                Sgl_setnegativezero(resultp1); 
        else Sgl_setzero(resultp1);

        /*
         * Generate multiply exponent 
         */
        mpy_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;

        /*
         * check first operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd1)) {
                if (Sgl_iszero_mantissa(opnd1)) {
                        if (Sgl_isnotnan(opnd2) && Sgl_isnotnan(opnd3)) {
                                if (Sgl_iszero_exponentmantissa(opnd2)) {
                                        /* 
                                         * invalid since operands are infinity 
                                         * and zero 
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }
                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Sgl_isinfinity(opnd3) &&
                                    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Sgl_setinfinity_exponentmantissa(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled()) 
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd1);
                        }
                        /* 
                         * is second operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd2)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd2);
                                Sgl_copytoptr(opnd2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                                Sgl_copytoptr(opnd3,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd1,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check second operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd2)) {
                if (Sgl_iszero_mantissa(opnd2)) {
                        if (Sgl_isnotnan(opnd3)) {
                                if (Sgl_iszero_exponentmantissa(opnd1)) {
                                        /* 
                                         * invalid since multiply operands are
                                         * zero & infinity
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(opnd2);
                                        Sgl_copytoptr(opnd2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Sgl_isinfinity(opnd3) &&
                                    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Sgl_setinfinity_exponentmantissa(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd2)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd2);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                                Sgl_copytoptr(opnd3,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check third operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd3)) {
                if (Sgl_iszero_mantissa(opnd3)) {
                        /* return infinity */
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                } else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * Generate multiply mantissa
         */
        if (Sgl_isnotzero_exponent(opnd1)) {
                /* set hidden bit */
                Sgl_clear_signexponent_set_hidden(opnd1);
        }
        else {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd1)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Sgl_iszero_exponentmantissa(opnd3)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Sgl_or_signs(opnd3,resultp1);
                                } else {
                                        Sgl_and_signs(opnd3,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Sgl_iszero_exponent(opnd3) &&
                                 Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Sgl_signextendedsign(opnd3);
                                result_exponent = 0;
                                Sgl_leftshiftby1(opnd3);
                                Sgl_normalize(opnd3,result_exponent);
                                Sgl_set_sign(opnd3,/*using*/sign_save);
                                Sgl_setwrapped_exponent(opnd3,result_exponent,
                                                        unfl);
                                Sgl_copytoptr(opnd3,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized, adjust exponent */
                Sgl_clear_signexponent(opnd1);
                Sgl_leftshiftby1(opnd1);
                Sgl_normalize(opnd1,mpy_exponent);
        }
        /* opnd2 needs to have hidden bit set with msb in hidden bit */
        if (Sgl_isnotzero_exponent(opnd2)) {
                Sgl_clear_signexponent_set_hidden(opnd2);
        }
        else {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd2)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Sgl_iszero_exponentmantissa(opnd3)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Sgl_or_signs(opnd3,resultp1);
                                } else {
                                        Sgl_and_signs(opnd3,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Sgl_iszero_exponent(opnd3) &&
                            Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Sgl_signextendedsign(opnd3);
                                result_exponent = 0;
                                Sgl_leftshiftby1(opnd3);
                                Sgl_normalize(opnd3,result_exponent);
                                Sgl_set_sign(opnd3,/*using*/sign_save);
                                Sgl_setwrapped_exponent(opnd3,result_exponent,
                                                        unfl);
                                Sgl_copytoptr(opnd3,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized; want to normalize */
                Sgl_clear_signexponent(opnd2);
                Sgl_leftshiftby1(opnd2);
                Sgl_normalize(opnd2,mpy_exponent);
        }

        /* Multiply the first two source mantissas together */

        /* 
         * The intermediate result will be kept in tmpres,
         * which needs enough room for 106 bits of mantissa,
         * so lets call it a Double extended.
         */
        Sglext_setzero(tmpresp1,tmpresp2);

        /* 
         * Four bits at a time are inspected in each loop, and a 
         * simple shift and add multiply algorithm is used. 
         */ 
        for (count = SGL_P-1; count >= 0; count -= 4) {
                Sglext_rightshiftby4(tmpresp1,tmpresp2);
                if (Sbit28(opnd1)) {
                        /* Twoword_add should be an ADD followed by 2 ADDC's */
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<3, 0);
                }
                if (Sbit29(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<2, 0);
                }
                if (Sbit30(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<1, 0);
                }
                if (Sbit31(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2, 0);
                }
                Sgl_rightshiftby4(opnd1);
        }
        if (Is_sexthiddenoverflow(tmpresp1)) {
                /* result mantissa >= 2 (mantissa overflow) */
                mpy_exponent++;
                Sglext_rightshiftby4(tmpresp1,tmpresp2);
        } else {
                Sglext_rightshiftby3(tmpresp1,tmpresp2);
        }

        /*
         * Restore the sign of the mpy result which was saved in resultp1.
         * The exponent will continue to be kept in mpy_exponent.
         */
        Sglext_set_sign(tmpresp1,Sgl_sign(resultp1));

        /* 
         * No rounding is required, since the result of the multiply
         * is exact in the extended format.
         */

        /*
         * Now we are ready to perform the add portion of the operation.
         *
         * The exponents need to be kept as integers for now, since the
         * multiply result might not fit into the exponent field.  We
         * can't overflow or underflow because of this yet, since the
         * add could bring the final result back into range.
         */
        add_exponent = Sgl_exponent(opnd3);

        /*
         * Check for denormalized or zero add operand.
         */
        if (add_exponent == 0) {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd3)) {
                        /* right is zero */
                        /* Left can't be zero and must be result.
                         *
                         * The final result is now in tmpres and mpy_exponent,
                         * and needs to be rounded and squeezed back into
                         * double precision format from double extended.
                         */
                        result_exponent = mpy_exponent;
                        Sglext_copy(tmpresp1,tmpresp2,resultp1,resultp2);
                        sign_save = Sgl_signextendedsign(resultp1);/*save sign*/
                        goto round;
                }

                /* 
                 * Neither are zeroes.  
                 * Adjust exponent and normalize add operand.
                 */
                sign_save = Sgl_signextendedsign(opnd3);        /* save sign */
                Sgl_clear_signexponent(opnd3);
                Sgl_leftshiftby1(opnd3);
                Sgl_normalize(opnd3,add_exponent);
                Sgl_set_sign(opnd3,sign_save);          /* restore sign */
        } else {
                Sgl_clear_exponent_set_hidden(opnd3);
        }
        /*
         * Copy opnd3 to the double extended variable called right.
         */
        Sgl_copyto_sglext(opnd3,rightp1,rightp2);

        /*
         * A zero "save" helps discover equal operands (for later),
         * and is used in swapping operands (if needed).
         */
        Sglext_xortointp1(tmpresp1,rightp1,/*to*/save);

        /*
         * Compare magnitude of operands.
         */
        Sglext_copytoint_exponentmantissa(tmpresp1,signlessleft1);
        Sglext_copytoint_exponentmantissa(rightp1,signlessright1);
        if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
            Sglext_ismagnitudeless(signlessleft1,signlessright1)) {
                /*
                 * Set the left operand to the larger one by XOR swap.
                 * First finish the first word "save".
                 */
                Sglext_xorfromintp1(save,rightp1,/*to*/rightp1);
                Sglext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
                Sglext_swap_lower(tmpresp2,rightp2);
                /* also setup exponents used in rest of routine */
                diff_exponent = add_exponent - mpy_exponent;
                result_exponent = add_exponent;
        } else {
                /* also setup exponents used in rest of routine */
                diff_exponent = mpy_exponent - add_exponent;
                result_exponent = mpy_exponent;
        }
        /* Invariant: left is not smaller than right. */

        /*
         * Special case alignment of operands that would force alignment
         * beyond the extent of the extension.  A further optimization
         * could special case this but only reduces the path length for
         * this infrequent case.
         */
        if (diff_exponent > SGLEXT_THRESHOLD) {
                diff_exponent = SGLEXT_THRESHOLD;
        }

        /* Align right operand by shifting it to the right */
        Sglext_clear_sign(rightp1);
        Sglext_right_align(rightp1,rightp2,/*shifted by*/diff_exponent);
        
        /* Treat sum and difference of the operands separately. */
        if ((int)save < 0) {
                /*
                 * Difference of the two operands.  Overflow can occur if the
                 * multiply overflowed.  A borrow can occur out of the hidden
                 * bit and force a post normalization phase.
                 */
                Sglext_subtract(tmpresp1,tmpresp2, rightp1,rightp2,
                        resultp1,resultp2);
                sign_save = Sgl_signextendedsign(resultp1);
                if (Sgl_iszero_hidden(resultp1)) {
                        /* Handle normalization */
                /* A straight foward algorithm would now shift the
                 * result and extension left until the hidden bit
                 * becomes one.  Not all of the extension bits need
                 * participate in the shift.  Only the two most 
                 * significant bits (round and guard) are needed.
                 * If only a single shift is needed then the guard
                 * bit becomes a significant low order bit and the
                 * extension must participate in the rounding.
                 * If more than a single shift is needed, then all
                 * bits to the right of the guard bit are zeros, 
                 * and the guard bit may or may not be zero. */
                        Sglext_leftshiftby1(resultp1,resultp2);

                        /* Need to check for a zero result.  The sign and
                         * exponent fields have already been zeroed.  The more
                         * efficient test of the full object can be used.
                         */
                         if (Sglext_iszero(resultp1,resultp2)) {
                                /* Must have been "x-x" or "x+(-x)". */
                                if (Is_rounding_mode(ROUNDMINUS))
                                        Sgl_setone_sign(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                        result_exponent--;

                        /* Look to see if normalization is finished. */
                        if (Sgl_isone_hidden(resultp1)) {
                                /* No further normalization is needed */
                                goto round;
                        }

                        /* Discover first one bit to determine shift amount.
                         * Use a modified binary search.  We have already
                         * shifted the result one position right and still
                         * not found a one so the remainder of the extension
                         * must be zero and simplifies rounding. */
                        /* Scan bytes */
                        while (Sgl_iszero_hiddenhigh7mantissa(resultp1)) {
                                Sglext_leftshiftby8(resultp1,resultp2);
                                result_exponent -= 8;
                        }
                        /* Now narrow it down to the nibble */
                        if (Sgl_iszero_hiddenhigh3mantissa(resultp1)) {
                                /* The lower nibble contains the
                                 * normalizing one */
                                Sglext_leftshiftby4(resultp1,resultp2);
                                result_exponent -= 4;
                        }
                        /* Select case where first bit is set (already
                         * normalized) otherwise select the proper shift. */
                        jumpsize = Sgl_hiddenhigh3mantissa(resultp1);
                        if (jumpsize <= 7) switch(jumpsize) {
                        case 1:
                                Sglext_leftshiftby3(resultp1,resultp2);
                                result_exponent -= 3;
                                break;
                        case 2:
                        case 3:
                                Sglext_leftshiftby2(resultp1,resultp2);
                                result_exponent -= 2;
                                break;
                        case 4:
                        case 5:
                        case 6:
                        case 7:
                                Sglext_leftshiftby1(resultp1,resultp2);
                                result_exponent -= 1;
                                break;
                        }
                } /* end if (hidden...)... */
        /* Fall through and round */
        } /* end if (save < 0)... */
        else {
                /* Add magnitudes */
                Sglext_addition(tmpresp1,tmpresp2,
                        rightp1,rightp2, /*to*/resultp1,resultp2);
                sign_save = Sgl_signextendedsign(resultp1);
                if (Sgl_isone_hiddenoverflow(resultp1)) {
                        /* Prenormalization required. */
                        Sglext_arithrightshiftby1(resultp1,resultp2);
                        result_exponent++;
                } /* end if hiddenoverflow... */
        } /* end else ...add magnitudes... */

        /* Round the result.  If the extension and lower two words are
         * all zeros, then the result is exact.  Otherwise round in the
         * correct direction.  Underflow is possible. If a postnormalization
         * is necessary, then the mantissa is all zeros so no shift is needed.
         */
  round:
        if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
                Sglext_denormalize(resultp1,resultp2,result_exponent,is_tiny);
        }
        Sgl_set_sign(resultp1,/*using*/sign_save);
        if (Sglext_isnotzero_mantissap2(resultp2)) {
                inexact = TRUE;
                switch(Rounding_mode()) {
                case ROUNDNEAREST: /* The default. */
                        if (Sglext_isone_highp2(resultp2)) {
                                /* at least 1/2 ulp */
                                if (Sglext_isnotzero_low31p2(resultp2) ||
                                    Sglext_isone_lowp1(resultp1)) {
                                        /* either exactly half way and odd or
                                         * more than 1/2ulp */
                                        Sgl_increment(resultp1);
                                }
                        }
                        break;

                case ROUNDPLUS:
                        if (Sgl_iszero_sign(resultp1)) {
                                /* Round up positive results */
                                Sgl_increment(resultp1);
                        }
                        break;
            
                case ROUNDMINUS:
                        if (Sgl_isone_sign(resultp1)) {
                                /* Round down negative results */
                                Sgl_increment(resultp1);
                        }
            
                case ROUNDZERO:;
                        /* truncate is simple */
                } /* end switch... */
                if (Sgl_isone_hiddenoverflow(resultp1)) result_exponent++;
        }
        if (result_exponent >= SGL_INFINITY_EXPONENT) {
                /* Overflow */
                if (Is_overflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(resultp1,result_exponent,ovfl);
                        Sgl_copytoptr(resultp1,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_OVERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return (OPC_2E_OVERFLOWEXCEPTION);
                }
                inexact = TRUE;
                Set_overflowflag();
                Sgl_setoverflow(resultp1);
        } else if (result_exponent <= 0) {      /* underflow case */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(resultp1,result_exponent,unfl);
                        Sgl_copytoptr(resultp1,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_UNDERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);

                            else Set_inexactflag();
                        return(OPC_2E_UNDERFLOWEXCEPTION);
                }
                else if (inexact && is_tiny) Set_underflowflag();
        }
        else Sgl_set_exponent(resultp1,result_exponent);
        Sgl_copytoptr(resultp1,dstptr);
        if (inexact) 
                if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
                else Set_inexactflag();
        return(NOEXCEPTION);
}

/*
 *  Single Floating-point Multiply Negate Fused Add
 */

sgl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)

sgl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
unsigned int *status;
{
        unsigned int opnd1, opnd2, opnd3;
        register unsigned int tmpresp1, tmpresp2;
        unsigned int rightp1, rightp2;
        unsigned int resultp1, resultp2 = 0;
        register int mpy_exponent, add_exponent, count;
        boolean inexact = FALSE, is_tiny = FALSE;

        unsigned int signlessleft1, signlessright1, save;
        register int result_exponent, diff_exponent;
        int sign_save, jumpsize;
        
        Sgl_copyfromptr(src1ptr,opnd1);
        Sgl_copyfromptr(src2ptr,opnd2);
        Sgl_copyfromptr(src3ptr,opnd3);

        /* 
         * set sign bit of result of multiply
         */
        if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) 
                Sgl_setzero(resultp1);
        else 
                Sgl_setnegativezero(resultp1); 

        /*
         * Generate multiply exponent 
         */
        mpy_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;

        /*
         * check first operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd1)) {
                if (Sgl_iszero_mantissa(opnd1)) {
                        if (Sgl_isnotnan(opnd2) && Sgl_isnotnan(opnd3)) {
                                if (Sgl_iszero_exponentmantissa(opnd2)) {
                                        /* 
                                         * invalid since operands are infinity 
                                         * and zero 
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }
                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Sgl_isinfinity(opnd3) &&
                                    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Sgl_setinfinity_exponentmantissa(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd1)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled()) 
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd1);
                        }
                        /* 
                         * is second operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd2)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd2);
                                Sgl_copytoptr(opnd2,dstptr);
                                return(NOEXCEPTION);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                                Sgl_copytoptr(opnd3,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd1,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check second operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd2)) {
                if (Sgl_iszero_mantissa(opnd2)) {
                        if (Sgl_isnotnan(opnd3)) {
                                if (Sgl_iszero_exponentmantissa(opnd1)) {
                                        /* 
                                         * invalid since multiply operands are
                                         * zero & infinity
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(opnd2);
                                        Sgl_copytoptr(opnd2,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * Check third operand for infinity with a
                                 *  sign opposite of the multiply result
                                 */
                                if (Sgl_isinfinity(opnd3) &&
                                    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
                                        /* 
                                         * invalid since attempting a magnitude
                                         * subtraction of infinities
                                         */
                                        if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                        Set_invalidflag();
                                        Sgl_makequietnan(resultp1);
                                        Sgl_copytoptr(resultp1,dstptr);
                                        return(NOEXCEPTION);
                                }

                                /*
                                 * return infinity
                                 */
                                Sgl_setinfinity_exponentmantissa(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                }
                else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd2)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd2);
                        }
                        /* 
                         * is third operand a signaling NaN? 
                         */
                        else if (Sgl_is_signalingnan(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                                return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                                Sgl_copytoptr(opnd3,dstptr);
                                return(NOEXCEPTION);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd2,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * check third operand for NaN's or infinity
         */
        if (Sgl_isinfinity_exponent(opnd3)) {
                if (Sgl_iszero_mantissa(opnd3)) {
                        /* return infinity */
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                } else {
                        /*
                         * is NaN; signaling or quiet?
                         */
                        if (Sgl_isone_signaling(opnd3)) {
                                /* trap if INVALIDTRAP enabled */
                                if (Is_invalidtrap_enabled())
                                        return(OPC_2E_INVALIDEXCEPTION);
                                /* make NaN quiet */
                                Set_invalidflag();
                                Sgl_set_quiet(opnd3);
                        }
                        /*
                         * return quiet NaN
                         */
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
        }

        /*
         * Generate multiply mantissa
         */
        if (Sgl_isnotzero_exponent(opnd1)) {
                /* set hidden bit */
                Sgl_clear_signexponent_set_hidden(opnd1);
        }
        else {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd1)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Sgl_iszero_exponentmantissa(opnd3)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Sgl_or_signs(opnd3,resultp1);
                                } else {
                                        Sgl_and_signs(opnd3,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Sgl_iszero_exponent(opnd3) &&
                                 Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Sgl_signextendedsign(opnd3);
                                result_exponent = 0;
                                Sgl_leftshiftby1(opnd3);
                                Sgl_normalize(opnd3,result_exponent);
                                Sgl_set_sign(opnd3,/*using*/sign_save);
                                Sgl_setwrapped_exponent(opnd3,result_exponent,
                                                        unfl);
                                Sgl_copytoptr(opnd3,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized, adjust exponent */
                Sgl_clear_signexponent(opnd1);
                Sgl_leftshiftby1(opnd1);
                Sgl_normalize(opnd1,mpy_exponent);
        }
        /* opnd2 needs to have hidden bit set with msb in hidden bit */
        if (Sgl_isnotzero_exponent(opnd2)) {
                Sgl_clear_signexponent_set_hidden(opnd2);
        }
        else {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd2)) {
                        /*
                         * Perform the add opnd3 with zero here.
                         */
                        if (Sgl_iszero_exponentmantissa(opnd3)) {
                                if (Is_rounding_mode(ROUNDMINUS)) {
                                        Sgl_or_signs(opnd3,resultp1);
                                } else {
                                        Sgl_and_signs(opnd3,resultp1);
                                }
                        }
                        /*
                         * Now let's check for trapped underflow case.
                         */
                        else if (Sgl_iszero_exponent(opnd3) &&
                            Is_underflowtrap_enabled()) {
                                /* need to normalize results mantissa */
                                sign_save = Sgl_signextendedsign(opnd3);
                                result_exponent = 0;
                                Sgl_leftshiftby1(opnd3);
                                Sgl_normalize(opnd3,result_exponent);
                                Sgl_set_sign(opnd3,/*using*/sign_save);
                                Sgl_setwrapped_exponent(opnd3,result_exponent,
                                                        unfl);
                                Sgl_copytoptr(opnd3,dstptr);
                                /* inexact = FALSE */
                                return(OPC_2E_UNDERFLOWEXCEPTION);
                        }
                        Sgl_copytoptr(opnd3,dstptr);
                        return(NOEXCEPTION);
                }
                /* is denormalized; want to normalize */
                Sgl_clear_signexponent(opnd2);
                Sgl_leftshiftby1(opnd2);
                Sgl_normalize(opnd2,mpy_exponent);
        }

        /* Multiply the first two source mantissas together */

        /* 
         * The intermediate result will be kept in tmpres,
         * which needs enough room for 106 bits of mantissa,
         * so lets call it a Double extended.
         */
        Sglext_setzero(tmpresp1,tmpresp2);

        /* 
         * Four bits at a time are inspected in each loop, and a 
         * simple shift and add multiply algorithm is used. 
         */ 
        for (count = SGL_P-1; count >= 0; count -= 4) {
                Sglext_rightshiftby4(tmpresp1,tmpresp2);
                if (Sbit28(opnd1)) {
                        /* Twoword_add should be an ADD followed by 2 ADDC's */
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<3, 0);
                }
                if (Sbit29(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<2, 0);
                }
                if (Sbit30(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2<<1, 0);
                }
                if (Sbit31(opnd1)) {
                        Twoword_add(tmpresp1, tmpresp2, opnd2, 0);
                }
                Sgl_rightshiftby4(opnd1);
        }
        if (Is_sexthiddenoverflow(tmpresp1)) {
                /* result mantissa >= 2 (mantissa overflow) */
                mpy_exponent++;
                Sglext_rightshiftby4(tmpresp1,tmpresp2);
        } else {
                Sglext_rightshiftby3(tmpresp1,tmpresp2);
        }

        /*
         * Restore the sign of the mpy result which was saved in resultp1.
         * The exponent will continue to be kept in mpy_exponent.
         */
        Sglext_set_sign(tmpresp1,Sgl_sign(resultp1));

        /* 
         * No rounding is required, since the result of the multiply
         * is exact in the extended format.
         */

        /*
         * Now we are ready to perform the add portion of the operation.
         *
         * The exponents need to be kept as integers for now, since the
         * multiply result might not fit into the exponent field.  We
         * can't overflow or underflow because of this yet, since the
         * add could bring the final result back into range.
         */
        add_exponent = Sgl_exponent(opnd3);

        /*
         * Check for denormalized or zero add operand.
         */
        if (add_exponent == 0) {
                /* check for zero */
                if (Sgl_iszero_mantissa(opnd3)) {
                        /* right is zero */
                        /* Left can't be zero and must be result.
                         *
                         * The final result is now in tmpres and mpy_exponent,
                         * and needs to be rounded and squeezed back into
                         * double precision format from double extended.
                         */
                        result_exponent = mpy_exponent;
                        Sglext_copy(tmpresp1,tmpresp2,resultp1,resultp2);
                        sign_save = Sgl_signextendedsign(resultp1);/*save sign*/
                        goto round;
                }

                /* 
                 * Neither are zeroes.  
                 * Adjust exponent and normalize add operand.
                 */
                sign_save = Sgl_signextendedsign(opnd3);        /* save sign */
                Sgl_clear_signexponent(opnd3);
                Sgl_leftshiftby1(opnd3);
                Sgl_normalize(opnd3,add_exponent);
                Sgl_set_sign(opnd3,sign_save);          /* restore sign */
        } else {
                Sgl_clear_exponent_set_hidden(opnd3);
        }
        /*
         * Copy opnd3 to the double extended variable called right.
         */
        Sgl_copyto_sglext(opnd3,rightp1,rightp2);

        /*
         * A zero "save" helps discover equal operands (for later),
         * and is used in swapping operands (if needed).
         */
        Sglext_xortointp1(tmpresp1,rightp1,/*to*/save);

        /*
         * Compare magnitude of operands.
         */
        Sglext_copytoint_exponentmantissa(tmpresp1,signlessleft1);
        Sglext_copytoint_exponentmantissa(rightp1,signlessright1);
        if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
            Sglext_ismagnitudeless(signlessleft1,signlessright1)) {
                /*
                 * Set the left operand to the larger one by XOR swap.
                 * First finish the first word "save".
                 */
                Sglext_xorfromintp1(save,rightp1,/*to*/rightp1);
                Sglext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
                Sglext_swap_lower(tmpresp2,rightp2);
                /* also setup exponents used in rest of routine */
                diff_exponent = add_exponent - mpy_exponent;
                result_exponent = add_exponent;
        } else {
                /* also setup exponents used in rest of routine */
                diff_exponent = mpy_exponent - add_exponent;
                result_exponent = mpy_exponent;
        }
        /* Invariant: left is not smaller than right. */

        /*
         * Special case alignment of operands that would force alignment
         * beyond the extent of the extension.  A further optimization
         * could special case this but only reduces the path length for
         * this infrequent case.
         */
        if (diff_exponent > SGLEXT_THRESHOLD) {
                diff_exponent = SGLEXT_THRESHOLD;
        }

        /* Align right operand by shifting it to the right */
        Sglext_clear_sign(rightp1);
        Sglext_right_align(rightp1,rightp2,/*shifted by*/diff_exponent);
        
        /* Treat sum and difference of the operands separately. */
        if ((int)save < 0) {
                /*
                 * Difference of the two operands.  Overflow can occur if the
                 * multiply overflowed.  A borrow can occur out of the hidden
                 * bit and force a post normalization phase.
                 */
                Sglext_subtract(tmpresp1,tmpresp2, rightp1,rightp2,
                        resultp1,resultp2);
                sign_save = Sgl_signextendedsign(resultp1);
                if (Sgl_iszero_hidden(resultp1)) {
                        /* Handle normalization */
                /* A straight foward algorithm would now shift the
                 * result and extension left until the hidden bit
                 * becomes one.  Not all of the extension bits need
                 * participate in the shift.  Only the two most 
                 * significant bits (round and guard) are needed.
                 * If only a single shift is needed then the guard
                 * bit becomes a significant low order bit and the
                 * extension must participate in the rounding.
                 * If more than a single shift is needed, then all
                 * bits to the right of the guard bit are zeros, 
                 * and the guard bit may or may not be zero. */
                        Sglext_leftshiftby1(resultp1,resultp2);

                        /* Need to check for a zero result.  The sign and
                         * exponent fields have already been zeroed.  The more
                         * efficient test of the full object can be used.
                         */
                         if (Sglext_iszero(resultp1,resultp2)) {
                                /* Must have been "x-x" or "x+(-x)". */
                                if (Is_rounding_mode(ROUNDMINUS))
                                        Sgl_setone_sign(resultp1);
                                Sgl_copytoptr(resultp1,dstptr);
                                return(NOEXCEPTION);
                        }
                        result_exponent--;

                        /* Look to see if normalization is finished. */
                        if (Sgl_isone_hidden(resultp1)) {
                                /* No further normalization is needed */
                                goto round;
                        }

                        /* Discover first one bit to determine shift amount.
                         * Use a modified binary search.  We have already
                         * shifted the result one position right and still
                         * not found a one so the remainder of the extension
                         * must be zero and simplifies rounding. */
                        /* Scan bytes */
                        while (Sgl_iszero_hiddenhigh7mantissa(resultp1)) {
                                Sglext_leftshiftby8(resultp1,resultp2);
                                result_exponent -= 8;
                        }
                        /* Now narrow it down to the nibble */
                        if (Sgl_iszero_hiddenhigh3mantissa(resultp1)) {
                                /* The lower nibble contains the
                                 * normalizing one */
                                Sglext_leftshiftby4(resultp1,resultp2);
                                result_exponent -= 4;
                        }
                        /* Select case where first bit is set (already
                         * normalized) otherwise select the proper shift. */
                        jumpsize = Sgl_hiddenhigh3mantissa(resultp1);
                        if (jumpsize <= 7) switch(jumpsize) {
                        case 1:
                                Sglext_leftshiftby3(resultp1,resultp2);
                                result_exponent -= 3;
                                break;
                        case 2:
                        case 3:
                                Sglext_leftshiftby2(resultp1,resultp2);
                                result_exponent -= 2;
                                break;
                        case 4:
                        case 5:
                        case 6:
                        case 7:
                                Sglext_leftshiftby1(resultp1,resultp2);
                                result_exponent -= 1;
                                break;
                        }
                } /* end if (hidden...)... */
        /* Fall through and round */
        } /* end if (save < 0)... */
        else {
                /* Add magnitudes */
                Sglext_addition(tmpresp1,tmpresp2,
                        rightp1,rightp2, /*to*/resultp1,resultp2);
                sign_save = Sgl_signextendedsign(resultp1);
                if (Sgl_isone_hiddenoverflow(resultp1)) {
                        /* Prenormalization required. */
                        Sglext_arithrightshiftby1(resultp1,resultp2);
                        result_exponent++;
                } /* end if hiddenoverflow... */
        } /* end else ...add magnitudes... */

        /* Round the result.  If the extension and lower two words are
         * all zeros, then the result is exact.  Otherwise round in the
         * correct direction.  Underflow is possible. If a postnormalization
         * is necessary, then the mantissa is all zeros so no shift is needed.
         */
  round:
        if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
                Sglext_denormalize(resultp1,resultp2,result_exponent,is_tiny);
        }
        Sgl_set_sign(resultp1,/*using*/sign_save);
        if (Sglext_isnotzero_mantissap2(resultp2)) {
                inexact = TRUE;
                switch(Rounding_mode()) {
                case ROUNDNEAREST: /* The default. */
                        if (Sglext_isone_highp2(resultp2)) {
                                /* at least 1/2 ulp */
                                if (Sglext_isnotzero_low31p2(resultp2) ||
                                    Sglext_isone_lowp1(resultp1)) {
                                        /* either exactly half way and odd or
                                         * more than 1/2ulp */
                                        Sgl_increment(resultp1);
                                }
                        }
                        break;

                case ROUNDPLUS:
                        if (Sgl_iszero_sign(resultp1)) {
                                /* Round up positive results */
                                Sgl_increment(resultp1);
                        }
                        break;
            
                case ROUNDMINUS:
                        if (Sgl_isone_sign(resultp1)) {
                                /* Round down negative results */
                                Sgl_increment(resultp1);
                        }
            
                case ROUNDZERO:;
                        /* truncate is simple */
                } /* end switch... */
                if (Sgl_isone_hiddenoverflow(resultp1)) result_exponent++;
        }
        if (result_exponent >= SGL_INFINITY_EXPONENT) {
                /* Overflow */
                if (Is_overflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(resultp1,result_exponent,ovfl);
                        Sgl_copytoptr(resultp1,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_OVERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return (OPC_2E_OVERFLOWEXCEPTION);
                }
                inexact = TRUE;
                Set_overflowflag();
                Sgl_setoverflow(resultp1);
        } else if (result_exponent <= 0) {      /* underflow case */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Sgl_setwrapped_exponent(resultp1,result_exponent,unfl);
                        Sgl_copytoptr(resultp1,dstptr);
                        if (inexact)
                            if (Is_inexacttrap_enabled())
                                return (OPC_2E_UNDERFLOWEXCEPTION |
                                        OPC_2E_INEXACTEXCEPTION);
                            else Set_inexactflag();
                        return(OPC_2E_UNDERFLOWEXCEPTION);
                }
                else if (inexact && is_tiny) Set_underflowflag();
        }
        else Sgl_set_exponent(resultp1,result_exponent);
        Sgl_copytoptr(resultp1,dstptr);
        if (inexact) 
                if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
                else Set_inexactflag();
        return(NOEXCEPTION);
}